Tunneling machines having impact type hammer cutting tools mounted on a rotatable workhead are, generally speaking, known in the art and it has been proposed, heretofore, to arrange the cutting tools about the workhead in a manner so that the entirety of the tunnel face will be worked on during each cycle of workhead rotation. It has also been proposed to arrange the cutting tools about the periphery of the workhead. These prior machines included suction means for exhausting or removing the cuttings from the tunnel face. However, a primary difficulty with these prior machines lies in the disposition of the tools about the workhead which, in turn, greatly affect the wear characteristics of the tools. That is, in the arrangement wherein the cutting tools are disposed about the periphery of the workhead, while allowing quick removal of the cuttings, a major drawback is arrangement of cutting tools about the working surface, which results in an uneven wearing of the cutting tools. As may be appreciated, with an arrangement such as this, the cutting tools will wear considerably quicker about their outer most edges as compared to the wear distributed to the inside edges. The uneven wear characteristics inherent with these machines results in time spent to replace worn tools and therefore valuable operating time is spent on maintenance of the machine.